Effect of acoustic clutter on prey detection by bats

Abstract

Bats that capture animal prey from substrates often emit characteristic echolocation calls that are short-duration, frequency-modulated (FM) and broadband. Such calls seem to be suited to locating prey in uncluttered habitats, including flying prey, but may be less effective for finding prey among cluttered backgrounds because echoes reflecting from the substrate mask the acoustic signature of prey. Perhaps these call designs serve primarily for spatial orientation. Furthermore, it has been unclear whether the acoustic image conveyed by FM echoes enables fine texture discrimination, or whether gleaning bats that forage in echo-cluttering environments must locate prey by using other cues, such as prey-generated sounds. Here we show that two species of insectivorous gleaning bats perform badly when compelled to detect silent and immobile prey in clutter, but are very efficient at capturing noisy prey items among highly cluttered backgrounds, and both dead or live prey in uncluttered habitats. These findings suggest that the short, broadband FM echolocation calls associated with gleaning bats are not adapted to detecting prey in clutter.

Prey Selection byMyotis myotis(Vespertilionidae) in a Mediterranean Region

“…In fact, the main taxa, including carabids and some families of spiders (e.g., Lycosidae -Lang et al, 1999) that constituted the diet of M. myotis have intense nocturnal activity. Several authors suggested that sounds might increase the probability of prey detection by gleaning bats (Neuweiler, 1989;Faure and Barclay, 1992;Arlettaz et al, 2001), and prey calls are used by bats to locate potential victims (Belwood and Morris, 1987). The great conspicuousness of calling crickets may partly justify the selection pattern we have observed.…”

Coordination of bat sonar activity and flight for the exploration of three-dimensional objects

“…This is represented by the higher number of visited 10deg sectors of the VO and the higher number of emitted calls towards the selected VO. This is not due to a landing buzz [typical landing buzz interpulse intervals of 5-16ms (Arlettaz et al, 2001;Russo et al, 2007;Melcon et al, 2007;Melcon et al, 2009)], which the bats did not typically emit (in our study the shortest interpulse intervals were greater than 20ms). Rather, this reflects an early decision for a VO that the bats then affirmed by flying around the VO of interest.…”

Analysis of the echolocation calis and morphometry of a population of Myotis chiloensis (Waterhouse, 1838) from the southern Chilean temperate forest

“…The calls are usually characterised as three phases (neuweiler, 2000;Schnitzler et al, 2003;Siles and Terán, 2007): a) Search calls: to detect prey, with a narrow frequency range and a longer duration; b) Approximation calls, with increased frequency range and shorter duration; and c) Calls of terminal phase (Feeding Buzz), heard when a bat attempts to capture prey, with decreased frequency range and minimum duration (Kalko and Schnitzler, 1989). This last phase is not observed in bats that obtain their food from the ground, like some Myotis spp., as in this case, they are guided by the sounds emitted by the prey (Arlettaz et al, 2001). The terminal phase is typical of species specialised in hunting airborne prey (Siemers and Schnitzler, 2004).…”